1. Field of the Invention
This invention relates to a photosensitive semiconductor device, and particularly to a photocoupler having a photoemitting device and a photo-detecting device shaped in integral form.
2. Description of the Related Art
FIG. 4 is a view showing a section structure of a previously-used photocoupler. The prior art photocoupler will be explained below with reference to FIG. 4.
In FIG. 4, reference numerals 1 and 2 indicate a lead frame on the photo- or light-emission side and a lead frame on the photo- or light-reception side, respectively. A light- or photo-emitting device 3 and a light- or photo-receiving or -detecting device 4 are fixed to islands of the lead frames 1 and 2 respectively. Designated at numeral 5 shown in FIG. 4 is a light-transmissive or translucent resin, which couples the photo-emitting device 3 and the photo-detecting device 4 to each other in an opposed state. Further, they are resin-sealed with an epoxy molding resin to prevent external random light.
FIGS. 5(A) and 5(B) are respectively views showing configurations of conventional lead frame 1 on the light-emission side and lead frame 2 on the light-reception side. FIG. 6 is a view illustrating the manner of charging of the translucent resin 5. A method of manufacturing the photocoupler shown in FIG. 4 will be explained below with reference to FIGS. 5 and 6.
A photo-emitting device 3 and a photo-detecting device 4 are fixed to diagonally-shaded regions of islands of the lead frames shown in FIGS. 5(A) and 5(B).
Thereafter, the lead frame 1 with the photo-emitting device 3 placed thereon and the lead frame 2 with the photo-detecting device 4 placed thereon are placed as opposed to each other as shown in FIG. 6. In this condition, the translucent resin 5 is filled between the lead frame 1 and the lead frame 2 from diagonally above the lead frame 1 by the use of a dispenser 7 to thereby couple the photo-emitting device 3 and the photo-detecting device 4 to each other.
Thereafter, the whole part is plastic-sealed with a mold sealing material 6 to create the photocoupler shown in FIG. 4.
However, the conventional photocoupler has a problem in that upon fabrication of the photocoupler, the translucent resin 5 to be filled adheres to an upper surface (corresponding to a surface not opposed to the lead frame 2 on the light-emission side) of the lead frame 1 due to a subtle position displacement of the dispenser 7 for filling the translucent resin 5 (this state is indicated by a circle mark in FIG. 6).
As a result, the shape of the translucent resin 5 varies according to the position of the dispenser 7. This type of photocoupler has a problem in that since light reflected from an interface between the translucent resin 5 and the molding resin 6 is detected by the photo-detecting device 4, the efficiency of light transmission by the photocoupler varies as the translucent resin 5 changes in shape.
Further, a problem also arises in that the adhesion between the lead frame 1 and the molding resin 6 is deteriorated due to the attachment of the translucent resin 5 to the upper surface of the lead frame 1.